Photodevelopable direct print compositions comprising iodocadmates in admixture with silver halides

ABSTRACT

PHOTODEVELOPABLE DIRECT-PRINT SILVER HALIDE COMPOSITIONS COMPRISING IODOCADMATES, FOR EXAMPLE-POTASSIUM IODOCAMATE, EXHIBIT IMPROVED PHOTOGRAPHIC PROPERTIES, SUCH AS IMPROVED SPEED. IN ONE EMBODIMENT DIRECT-PRINT COMPOSITIONS COMPRISE AN IODOCADMATE IN COMBINATION WITH A CUPROUS HALIDE.

United States Patent Int. Cl. G03c ]/28 US. Cl. 96-408 8 Claims ABSTRACT OF THE DISCLOSURE Photodevelopable direct-print silver halide compositions comprising iodocadmates, for example-potassium iodocamate, exhibit improved photographic properties, such as improved speed. In one embodiment direct-print compositions comprise an iodocadmate in combination with a cuprous halide.

This invention relates to radiation-sensitive compositions and to photographic materials prepared therefrom. In one aspect this invention relates to new direct-print materials. In another aspect this invention relates to silver halide compositions containing an iodocadmate.

It is known in the art to make direct-print silver halide compositions. Belgian Pat. 649,463, issued July 15, 1964, is exemplary of one type of direct-print silver halide composition comprising cuprous ions.

It is desirable to increase the speed of photographic compositions for certain applications where exposure times are short, i.e., such as in an oscillograph recorder. Also it is desirable to increase image discrimination (D -D in direct-piint image records.

Therefore, it is an object of this invention to provide new photographic compositions.

It is another object of this invention to provide directprint materials.

It is another object of this invention to provide directprint compositions having increased photographic speed.

We have now found that these and other objects of the invention can be accomplished by the use of an iodocadmate. In one embodiment, direct-print compositions containing said iodocadmates exhibit improved photographic properties such as writing speed. In one embodiment direct-print emulsions comprising a cuprous salt in combination with an iodocadmate exhibit improved image discrimination (AD).

The silver halide of the present compositions can be prepared in the absence of a colloidal binder, or can be precipitated in an aqueous dispersion of a colloidal binder (i.e., a photographic silver halide emulsion). The silver halide compositions are prepared by methods which yield internal image emulsions. Such methods are described in US. Pat. 2,592,250; Glafkides, Photographic Chemistry, vol. 1, pp. 31-2, Fountain Press, London; Sutherns, US. Pat. 3,260,605 issued July 12, 1966; and McBride US. Pat. 3,287,137 issued Nov. 22, 1966, and 3,271,157 issued Sept. 6, 1966, wherein is disclosed the preparation of silver halide emulsions with organic thioether silver halide solvents present during the grain growth of the silver halide. Generally, about .1 to g. of such thioethers per mole of silver halide are used. Typical of such thioethers are 3,6-dithia-l,8-octanediol, 1,10-dithia-4,7,13,16-tetraoxacyclooctadecane, 7,10-diaza-1,l6-dicarboxamido-3,14-dithiahexadecane-6,l1-dione, and 1,l7-di-(N-ethylcarbamyl) -6,12-dithia-9-oxaheptadecane. Water soluble thiocyanates can also be used alone or in combination with thioethers during the precipitation of the silver halide. Typical useful thiocyanates are the alkali metal thiocyanates such as sodium thiocyanate and potassium thiocyanate.

The so-called internal image emulsions are useful in the invention. Such emulsions are prepared with silver halide grains wherein a substantial amount, and preferably a predominant amount, of the sensitivity to radiation (light, X-rays, electrons, etc.) is internal to the grains. Typically, such internal image emulsions are those which, when measured according to normal photographic techniques by coating a test portion of the emulsion on a transparent support, exposing to a light intensity scale having a fixed time between 1 10 and 1 second, bleaching 5 minutes in a 0.3% potassium ferr'icyanide solution at 65 F. and developing for about 5 minutes at 65 F. in Developer B below (an internal-type developer), have a sensitivity, measured at a density of 0.1 above fog, greater than the sensitivity of an identical test portion which has been exposed in the same way and developed for 6 minutes at 68 F. in Developer A below (a surface-type developer).

DEVELOPER A G. N-methyl-p-aminophenol sulfate 0.31 Sodium sulfite, dessicated 39.60 Hydroquinone 6.00 Sodium carbonate, desiccated 18.70 Potassium bromide 0.86 Citric acid 0.68 Potassium metabisulfite 1.50 Water to make 1 liter.

DEVELOPER B G. N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Sodium thiosulfate 10.0

Water to make 1 liter.

Silver halide for a light-sensive composition of the invention can also be prepared simply by mixing, in the absence of actinic radiation, aqueous solutions containing the necessary silver and halide ions. Silver nitrate is a convenient source of silver ions, and the sodium and potassium halide salts are convenient halides. The precipitate obtained can be wet, or dried to a powder.

It is preferred to prepare the silver halide by the conversion method as described below. In accordance with the conversion method of making silver halide including a bromide moiety, a precipitate ot the silver halide more water-soluble than silver bromide (e.g., silver chloride or a silver chlorobromide) is formed in an acidic aqueous medium by mixing a water-soluble salt of silver and a suitable water-soluble halide, the mixing time not being critical, with times ranging from 15 seconds to 3 hours being typical. The pH of the acidic aqueous ripening medium is preferably less than 4 and can be around 2 or lower. The resulting silver halide precipitate is converted to silver bromide in the presence of a water-soluble thiocyanate and a water-soluble bromide-containing halide. Conversion conditions are preferably chosen which favor ripening, and the temperature is typically maintained at an elevated temperature of at least 60 C. and preferably from 65 to C. The water-soluble thiocyanate is added to the aqueous acidic medium at any stage up to, or during, the conversion of the grains. The conversion to the silver bromide is more generally effected over a period of from 10 minutes to 2 hours.

When a silver halide emulsion is made by the conversion method described above, the making conditions are preferably chosen in accordance with those described above. It is preferable to use a photographically inert gelatin in preparing the emulsions. The mean projective area of the silver halide grains of such emulsions is generally between about .6 and 2.5 square microns, such emulsions being characterized as coarse-grained.

The silver halide of the light-sensitive compositions of this invention contains at least about 70 mole percent of bromide and is preferably silver bromide, a silver bromoiodide or a mixture of these. When iodide is present, it is preferred for the amount not to exceed 6 percent of the weight of the halide, and a maximum of 1 percent is particularly preferred. If chloride is present in the halide, this is preferably not in excess of about 30 mole percent because of the propensity of silver chloride to print-out rapidly. A small amount of lead ions, for example, approximately 0.25 mole percent, can usefully be included in the silver halide, and this can conveniently be incorporated by dissolving a plumbous salt such as lead nitrate in the silver salt solution used for the preparation of the halide.

Although the silver halide compositions are generally made with an equivalent or slight excess of halide ion present, we have found it desirable to add additional water-soluble iodide to the silver halide compositions after its precipitation. More generally, about .1 to 50 mole percent, and preferably about 1 to 10 mole percent of water-soluble iodide based on the silver halide emulsion is used. Illustrative water-soluble iodides include ammonium, calcium, lithium, magnesium, potassium, or sodium iodide.

The iodocadmates preferred in one embodiment of this invention include sodium iodocadmate, potassium iodocadmate and the like. Other iodocadmates such as calcium iodocadmate, ammonium iodocadmate, and the like can also be utilized in compositions of the invention. Generally, said iodocadmates are utilized in the silver halide compositions in concentrations of about 5 to about 150 grams per mole of silver and preferably in about 15 to about 70 grams per mole of silver.

Cuprous salts useful in the invention include salts such as cuprous bromide, cuprous chloride, cuprous thiocyanate, and preferably cuprous iodide. The cuprous salts can be added to the silver halide as a powder, as a suspension in a liquid such as water or an aqueous dispersion of a colloidal binder, or as a solution in a solvent such as acetonitrile, for example. Instead of pure solid cuprous salts, a solid solution of, for example, cuprous iodide in another salt, silver iodide, for example, can be added. In the case of the preferred embodiment, cuprous iodide concentrations to be added to the silver halide are between about 3 and about 100 grams of cuprous iodide per mole of silver halide. Lower or higher concentrations have useful effects, however, the above cuprous iodide concentrations are particularly useful for improving the photodevelopment, direct-print properties such as discrimination between image and background areas of the present silver halide precipitates or compositions containing substantially no vehicle.

If both the iodocadmates and the silver halide are powders, they can be mixed together using a pestle and mortar or a ball-mill. The mixture can then be mixed with any further additives needed for preparing the lightsensitive layers. If only the alkali metal iodocadmate 1s a powder, this can be stirred into a suspension or dispersion of the silver halide in Water or in a dispersion of the colloidal binder.

The light-sensitive compositions of this invention can be coated by convenient techniques on a photographic support to provide useful photodevelopable, direct-print materials. Typical suitable supports include paper, polyethylene-coated paper, cellulose acetate film, polystyrene film, polyethylene terephthalate film or the like.

A simple method of coating suitable for a composition in powder form is to rub the powder over the surface of an adhesive layer coated on a support; a transparent adhesive tape can conveniently be used. Another method of coating a powdered composition comprises dispersing it in a solution of a colloidal solution of polystyrene, and then applying a layer of the dispersion to the support.

To produce a photographic image with a sensitive material of the invention, the light-sensitive layer of the material is first exposed to a high intensity light image. When the latter is a trace produced by the movement of an oscillograph spot, the effective exposure time is commonly within the range of 0.1 to 100 microseconds. A typical instrument for exposing the photographic materials of the invention is an oscillograph as described in U.S. Pat 2,580,427, The latent image so produced is then photodeveloped by an overall exposure of the light-sensitive layer to relatively low intensity illumination such as with a conventional fluorescent light. a tungsten light or even ordinary daylight. A typical low-intensity illumination for carrying out the photodevelopment has an intensity of about lumens per square foot. Heat is desirably utilized during the photodevelopment step. Typically the subject emulsions are heated to a temperature of about 90 C. to 200 C. for about 1 to 30 seconds and photodeveloped after the initial high intensity exposure.

This invention can be further illustrated by the following examples of prefrered embodiments thereof although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

EXAMPLE 1 An aqueous solution containing 390 grams of silver nitrate is added to an aqueous solution containing 300 grams of potassium bromide with vigorous stirring. The precipitated silver bromide is filtered, washed and dried.

A 20 gram portion of the silver bromide is ground in a mortar with 1.0 gram of K CdI -2H O. An adhesive, pressure sensitive tape is pressed into the ground mixture to form a layer thereon.

A second sample is prepared by grinding a 20 gram portion of silver bromide with 1.0 gram of CuI. This sample is pressed onto an adhesive tape.

The respective strips are exposed on a sensitometer to a 10 second flash through a clear channel in one area and a blue (Wratten 35+38A Filter) channel, modulated by a AD=0.15 step tablet in a second area. They are then photodeveloped for nine minutes under an intensity of 35 foot-candles of cool-white fluorescent light.

Clear exposure Blue exposure No. of Approx. N0. of Approx. visible rel. visible rel.

steps speed steps speed Addenda Oul' 13 100 9 100 K2CdI4.2H2O 21+ 1, 600 21+ 6, 400+ EXAMPLE 2 Senitometric Discrimination exposure exposure N0. of Approx. visible rel. Addenda steps speed Dmi'ix Dmin D Gulf 14 0. 59 0.25 0. 34 KzCdIi. 2H2O 21+ 1,100+ 0. 42 0.18 0. 21 CuI-l-KaCdIr. 2H2O 19 562 0.72 0.21 0. 54

The combination of the iodocadmate with the cuprous halide provide high speed with high discrimination in the image record.

Similar results are obtained when sodium iodocadmate is used in the composition.

EXAMPLE 3 N0. of Approx visible iel Addenda (g. per g. AgBr) steps speed Control 11 100 KI (0. 024) 13 200 can 0. 02s 16 562 20 KI (0.0.24)+Cd12 (0. 26) 21+ 3,200+ KQOdLl. 211: 21+ 3, 200+ The combination of the KI and Cdi as used in the present sample provides a synergistic speed eifect greater than the simple addition of the component parts.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected Within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A photodevelopable direct-print composition comprising an iodocadmate salt in admixture with a silver halide wherein at least mole percent of said silver halide is silver bromide.

2. A composition according to claim 1 wherein said iodocadmate salt is selected from the group consisting of potassium, sodium, calcium, and ammonium iodocadmates.

3. A composition according to claim 2 further comprising a cuprous halide.

4. A composition according to claim 1 wherein said iodocadmate salt is potassium iodocadrnate.

5. A composition according to claim 4 comprising from about 5 to about 150 grams of potassium iodocadmate per mole of silver halide.

6. A composition according to claim 4 further compris ing a cuprous halide.

7. A composition according to claim 4 further comprising cuprous iodide.

8. A composition according to claim 5, further comprising from about 3 to about grams of cuprous iodide per mole of silver halide.

References Cited UNITED STATES PATENTS 3,033,682 5/1962 Hunt 96l08 3,109,737 11/1963 Scott 96108 3,420,669 1/1969 Suthern et a1. 96-108 NORMAN G. TORCHIN, Primary Examiner R. E. FIGHTER, Assistant Examiner 

